Asthma changes characteristic

Three Singapore patients with chronic arsenic poisoning with characteristic skin changes had taken Chinese herbal remedies for many years to treat their asthma two had cancers likely to be due to arsenic (150). 

A patient examined during an asthmatic attack will exhibit definite changes in pulmonary function, most predominantly decreases in expiratory flow rate as assessed by decreases in FEV j and the maximal expiratory flow at 50 and 25% of vital capacity (see Figs. 11 and 12). Since a characteristic feature of mild asthma is its reversibility, the reversibility of these changes in pulmonary function by a 1% nebulized solution of isoproterenol administered to the patient is also a diagnostic characteristic of asthma. 

Although the reversibility of airways obstruction is an important characteristic of asthma, those asthmatics with chronic symptoms do not reverse completely. The chronic airways obstruction is probably related to mucus plugging of bronchi and hypertrophy of the bronchial smooth muscle. These changes are not reversible by bronchodilators, and it is not clear that they can be reversed with any specific therapy. Both types of obstruction contribute to an imbalance of the ventilation to perfusion ratio in the lung and can result in hypoxemia and hypocarbia. The decreased carbon dioxide content of the blood is the result of the asthmatic s hyperventilation and will persist until the respiratory muscles fatigue and hypoventilation becomes prominent. Asthmatics can die quite quickly when this occurs. 

Several individual factors may also influence the variability of asthma. Poor inhaler technique for both metered-dose and dry powder inhalers is often observed in asthma patients and may be the cause for an increased risk of death. Further, personnel characteristics may also be the cause for the changes in lung functions. In healthy individuals, lung function exhibits a circadian rhythm. However, this will be changed in the individuals those who have nocturnal asthma. Moreover, obesity may also be a risk factor for asthma. Further, women may experience premenstrual and perimenstrual worsening of asthma symptoms. Asthma symptoms may be also triggered by exercise. 

Another characteristic feature in asthma is airway wall remodeling. This refers to a variety of structural changes in the airway wall. Most prominent is the accumulation of a band of t5 e III and t5 e V collagens (Hoshino et ah, 1998) and other matrix components in the subepithelial region of the airway wall. Airway wall thickening and shortening of airway smooth muscle may occur and these may cause airway resistance. 

Asthma is a common disease affecting approx 10% of the population in developed countries, and the prevalence and mortality are rising. The disease has characteristic symptoms, namely intermittent airway obstruction, airway hyperresponsiveness, and increased numbers of activated inflammatory cells and airway structural changes as a result of chronic airway inflammation. The primary underlying abnormality in bronchial asthma is thought to be the unique form of airway inflammation, including particularly eosinophils and mast cells, that gives rise to reversible airway obstruction and hyperresponsiveness. 

---